U.S. patent number 8,089,686 [Application Number 12/578,939] was granted by the patent office on 2012-01-03 for electronic display device providing static grayscale image.
This patent grant is currently assigned to Hewlett-Packard Development Company, L.P.. Invention is credited to Cary G. Addington, Jong-Souk Yeo.
United States Patent |
8,089,686 |
Addington , et al. |
January 3, 2012 |
Electronic display device providing static grayscale image
Abstract
In one embodiment, a device includes a first display element
including: a first electrode; a transparent dielectric layer having
recessed regions therein over the first electrode; a halftoned
second electrode opposite the first electrode; and a fluid with
colorant particles between the first electrode and the second
electrode, wherein a voltage signal applied between the first
electrode and the second electrode controls movement of the
colorant particles such that a first voltage signal provides a
clear optical state by compacting the colorant particles into the
recessed regions and a second voltage signal provides a grayscale
optical state by attracting the colorant particles to the second
electrode.
Inventors: |
Addington; Cary G. (Albany,
OR), Yeo; Jong-Souk (Corvallis, OR) |
Assignee: |
Hewlett-Packard Development
Company, L.P. (Houston, TX)
|
Family
ID: |
43854639 |
Appl.
No.: |
12/578,939 |
Filed: |
October 14, 2009 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20110085224 A1 |
Apr 14, 2011 |
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Current U.S.
Class: |
359/296;
345/107 |
Current CPC
Class: |
G02F
1/167 (20130101) |
Current International
Class: |
G02B
26/00 (20060101); G09G 3/34 (20060101) |
Field of
Search: |
;359/296,238 ;345/107
;430/32 ;204/600 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Choi; William
Claims
What is claimed is:
1. A device comprising: a first display element comprising: a first
electrode; a transparent dielectric layer having recessed regions
therein over the first electrode; a halftoned second electrode
opposite the first electrode; and a fluid with colorant particles
between the first electrode and the second electrode, wherein a
voltage signal applied between the first electrode and the second
electrode controls movement of the colorant particles such that a
first voltage signal provides a clear optical state by compacting
the colorant particles into the recessed regions and a second
voltage signal provides a grayscale optical state by attracting the
colorant particles to the second electrode, and wherein a third
voltage signal applied between the first electrode and the second
electrode provides a dark optical state by dispersing the colorant
particles between the first electrode and the second electrode.
2. The device of claim 1, wherein the second electrode comprises a
transparent conductor.
3. The device of claim 1, wherein the recessed regions in the
dielectric layer form a pattern of dots when viewed in plan.
4. The device of claim 1, wherein the first electrode comprises a
segmented electrode.
5. The device of claim 1, wherein the first electrode comprises a
continuous electrode.
6. The device of claim 1, further comprising: a first substrate
supporting the first electrode; and a second substrate supporting
the second electrode.
7. The device of claim 6, wherein at least one of the first
substrate and the second substrate comprises a transparent
material.
8. A device comprising: a first display element comprising: a first
electrode; a transparent dielectric layer having recessed regions
therein over the first electrode; a halftoned second electrode
opposite the first electrode; a fluid with colorant particles
between the first electrode and the second electrode; a first
substrate supporting the first electrode; and a second substrate
supporting the second electrode, wherein a voltage signal applied
between the first electrode and the second electrode controls
movement of the colorant particles such that a first voltage signal
provides a clear optical state by compacting the colorant particles
into the recessed regions and a second voltage signal provides a
grayscale optical state by attracting the colorant particles to the
second electrode, and wherein the first substrate comprises a
reflective material.
9. A device comprising: a first display element comprising: a first
electrode; a transparent dielectric layer having recessed regions
therein over the first electrode; a halftoned second electrode
opposite the first electrode; and a fluid with colorant particles
between the first electrode and the second electrode, wherein a
voltage signal applied between the first electrode and the second
electrode controls movement of the colorant particles such that a
first voltage signal provides a clear optical state by compacting
the colorant particles into the recessed regions and a second
voltage signal provides a grayscale optical state by attracting the
colorant particles to the second electrode; and a second display
element stacked on the first display element to provide a
multicolor display device, the second display element comprising: a
first electrode; a dielectric layer having recessed regions therein
over the first electrode; a halftoned second electrode opposite the
first electrode; and a fluid with colorant particles between the
first electrode and the second electrode, wherein a voltage signal
applied between the first electrode and the second electrode
controls movement of the colorant particles such that a first
voltage signal provides a clear optical state by compacting the
colorant particles into the recessed regions and a second voltage
signal provides a grayscale optical state by attracting the
colorant particles to the second electrode.
10. A device comprising: a first electrode; a patterned dielectric
layer over the first electrode; a second electrode opposite the
first electrode; and a display volume comprising a fluid with
colorant particles between the first electrode and the second
electrode, wherein a voltage signal applied between the first
electrode and the second electrode controls movement of the
colorant particles such that a first voltage signal provides a
grayscale optical state by attracting portion of the colorant
particles to exposed portions of the first electrode while another
portion of the colorant particles, which are away from the exposed
portions of the first electrode, remain in the display volume, and
a second voltage signal provides a dark optical state by dispersing
the colorant particles between the first electrode and the second
electrode.
11. The device of claim 10, wherein the second electrode comprises
a transparent conductor.
12. The device of claim 10, further comprising: a reflector
adjacent the first electrode or the second electrode.
13. The device of claim 10, wherein the dielectric layer comprises
a non-uniform pattern of recesses.
14. A device comprising: a first electrode; a patterned dielectric
layer over the first electrode; a second electrode opposite the
first electrode; and a fluid with colorant particles between the
first electrode and the second electrode, wherein a voltage signal
applied between the first electrode and the second electrode
controls movement of the colorant particles such that a first
voltage signal provides a grayscale optical state by attracting at
least a portion of the colorant particles to exposed portions of
the first electrode and a second voltage signal provides a dark
optical state by dispersing the colorant particles between the
first electrode and the second electrode, wherein at least one of
the first electrode and the second electrode comprises a segmented
electrode, and wherein the fluid with colorant particles extends
uninterrupted over the segmented electrode.
15. A device comprising: a first electrode; a patterned dielectric
layer over the first electrode; a second electrode opposite the
first electrode; and a fluid with colorant particles between the
first electrode and the second electrode, wherein a voltage signal
applied between the first electrode and the second electrode
controls movement of the colorant particles such that a first
voltage signal provides a grayscale optical state by attracting at
least a portion of the colorant particles to exposed portions of
the first electrode and a second voltage signal provides a dark
optical state by dispersing the colorant particles between the
first electrode and the second electrode, wherein the first
electrode is patterned; wherein the dielectric layer comprises a
uniform pattern of recesses, and wherein the fluid with colorant
particles extends uninterrupted over the patterned first
electrode.
16. A method for producing a static grayscale image for an
electro-optical display device, the method comprising: applying a
conductor to a first substrate; removing portions of the conductor
to provide a patterned first electrode; joining the first substrate
and first electrode to a second substrate supporting a second
electrode and a dielectric layer over the second electrode, the
dielectric layer comprising recessed regions; filling a space
between the first electrode and the second electrode with a fluid
with colorant particles; and applying a first voltage signal
between the first electrode and the second electrode to produce a
static grayscale image by attracting the colorant particles onto
the patterned first electrode.
17. The method of claim 16, wherein removing portions for the
conductor comprises one of laser delamination and laser
ablation.
18. The method of claim 16, wherein removing portions for the
conductor comprises one of wet or dry etching and
photo-patterning.
19. The method of claim 16, wherein applying the conductor to the
first substrate comprises applying a transparent conductor to a
transparent first substrate.
20. The method of claim 16, wherein removing portions of the
conductor comprises removing portions of the conductor to provide a
halftoned patterned first electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This Application is related to U.S. patent application Ser. No.
12/411,828, entitled "ELECTRO-OPTICAL DISPLAY," filed Mar. 26,
2009, which is incorporated herein by reference.
BACKGROUND
Electrophoresis is the translation of charged objects in a fluid in
response to an electric field. Electrophoretic inks are useful as a
medium to enable bistable, low power types of displays.
Electrophoretic displays have been developed using a dyed fluid and
white particles sandwiched between parallel electrodes on top and
bottom substrates. When an electric field is applied transverse to
the substrates across the dyed fluid to translate the white
particles to the viewing surface, the display appears white. When
the electric field is reversed to translate the white particles
away from the viewing surface, the display appears the color of the
dyed fluid. Conventional segmentation of electrophoretic displays
provide set boundaries in which each segment appears white or the
color of the dyed fluid. This limits the representation of
displayed images since a static grayscale optical state is not
enabled by typical segmentation of electrophoretic displays. In
addition, conventional electrophoretic displays do not provide a
good color gamut for full color displays.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating one embodiment of convective flow
of colorant particles in a fluid of an electro-optical display.
FIG. 2A illustrates a cross-sectional view of one embodiment of a
dark optical state of an electro-optical display element.
FIG. 2B illustrates a cross-sectional view of one embodiment of a
clear optical state of an electro-optical display element.
FIG. 3A illustrates a cross-sectional view of one embodiment of a
clear optical state of an electro-optical display element.
FIG. 3B illustrates a cross-sectional view of one embodiment of a
dark optical state of an electro-optical display element.
FIG. 4A illustrates a top view of one embodiment of an
electro-optical display element including a segmented or pixelated
electrode.
FIG. 4B illustrates a cross-sectional view of one embodiment of an
electro-optical display element including a segmented or pixelated
electrode.
FIG. 5 illustrates one embodiment of a static grayscale patterning
technique for an electro-optical display device.
FIG. 6 illustrates another embodiment of a static grayscale
patterning technique for an electro-optical display device.
FIG. 7A illustrates a cross-sectional view of one embodiment of a
grayscale optical state of an electro-optical display element.
FIG. 7B illustrates a cross-sectional view of one embodiment of a
dark optical state of an electro-optical display element.
FIG. 7C illustrates a cross-sectional view of one embodiment of a
clear optical state of an electro-optical display element.
FIG. 8A illustrates a cross-sectional view of one embodiment of a
grayscale optical state of an electro-optical display element.
FIG. 8B illustrates a cross-sectional view of one embodiment of a
dark optical state of an electro-optical display element.
FIG. 8C illustrates a cross-sectional view of one embodiment of a
clear optical state of an electro-optical display element.
FIG. 9 illustrates a cross-sectional view of one embodiment of
stacking grayscaled primary colorant layers for full color static
images.
FIG. 10A illustrates a cross-sectional view of one embodiment of a
full color transmissive static display.
FIG. 10B illustrates a cross-sectional view of one embodiment of a
full color reflective static display.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the
accompanying drawings which form a part hereof, and in which is
shown by way of illustration specific embodiments in which the
disclosure may be practiced. In this regard, directional
terminology, such as "top," "bottom," "front," "back," "leading,"
"trailing," etc., is used with reference to the orientation of the
Figure(s) being described. Because components of embodiments can be
positioned in a number of different orientations, the directional
terminology is used for purposes of illustration and is in no way
limiting. It is to be understood that other embodiments may be
utilized and structural or logical changes may be made without
departing from the scope of the present disclosure. The following
detailed description, therefore, is not to be taken in a limiting
sense, and the scope of the present disclosure is defined by the
appended claims.
As used herein, the term "grayscale" applies to both black and
white images and monochromatic color images. Grayscale refers to an
image including different shades of a single color produced by
controlling the density of the single color within a given area of
a display.
As used herein, a "halftoned" electrode refers to an electrode
material layer that has been patterned or structured to enable a
grayscale image to be displayed. The electrode material layer is
structured to remove portions of the material such that only the
remaining portions of the material can attract colorant particles.
By controlling the amount of material remaining in a given area of
the electrode, a grayscale image can be displayed.
As used herein, the term "over" is not limited to any particular
orientation and can include above, below, next to, adjacent to,
and/or on. In addition, the term "over" can encompass intervening
components between a first component and a second component where
the first component is "over" the second component.
Embodiments provide static grayscale images using electro-optical
display devices. Full color static images are obtained by combining
multiple single color static grayscale images into a color display.
In one embodiment, to provide the static grayscale images, one or
both electrodes of the electro-optical display device are patterned
or halftoned. By removing specific areas/patterns of the electrode
material, the electronic inks spread onto the active areas of the
electrodes that are remaining on the substrate. By controlling the
ratio of the areas where charged colorant particles are present and
not present, grayscale is achieved. In this embodiment, a dark
optical state, a grayscale optical state, and a clear optical state
can be achieved.
In another embodiment, to provide the static grayscale images, a
dielectric layer over an electrode of the electro-streaming display
device is patterned. By removing specific areas/patterns of the
dielectric material, the electronic inks spread onto the exposed
areas of the electrode. By controlling the ratio of the exposed
areas to unexposed areas of the electrode, grayscale is achieved.
In this embodiment, a dark optical state and a grayscale optical
state can be achieved but a clear optical state cannot be
achieved.
In another embodiment, to provide the static grayscale images, a
dielectric layer over an electrode of the electro-optical display
device is patterned. By patterning the dielectric layer to include
non-patterned regions and specific areas/patterns of uniformly
recessed regions within the dielectric material, the electronic
inks can only compact into the recessed regions of the dielectric
layer. By controlling the ratio of the uniformly recessed regions
to the regions that are not recessed within the dielectric layer,
grayscale is achieved. In this embodiment, a dark optical state, a
grayscale optical state, and a clear optical state can be
achieved.
The embodiments encompass display elements having an energy
gradient that induces a convective flow according to a defined
pattern. The convective flow can be controlled so as to move a
colorant species that is affected by such an energy source. The
energy gradient is induced by methods including mechanical force, a
temperature gradient, a chemical potential gradient, a
concentration gradient, or other suitable disturbances. The present
embodiments can be manifested in an electro-optical application
where a means for inducing a convective flow includes electrodes,
electrokinetic elements, heating elements, microfluidic elements,
micro-electromechanical elements, or chemical reactions. Means for
controlling the convective flow (e.g., a patterned electrode and/or
a patterned dielectric layer to expose part of the electrodes)
provides an energy transfer, such as charge transfer, to control
the convective flow of the colorant species and thus the speed and
direction of the species.
The display elements subsequently described use both out-of-plane
movement as well as in-plane movement of colorant particles to
provide the desired optical appearance. Electrokinetic principles
of electro-convection and electrophoresis are used for an
electro-optical display to move charged colorant particles in a
carrier fluid within a display element. A display element can be a
pixel, a sub-pixel, a super-pixel, a segment, or other suitable
display element.
In general, a colorant particle may have a size between several
nanometers and several microns and has the property of changing the
spectral composition of the incident light by absorbing and/or
scattering certain portions of the spectrum. As a result, the
particle appears colored, which provides a desired optical effect.
In other embodiments, the colorant can be a dye, which is comprised
of single absorbing molecules.
FIG. 1 is a diagram illustrating one embodiment of convective flow
of colorant particles in a fluid of an electro-optical display
element 90. Display element 90 is a segment, a pixel, a sub-pixel,
a super pixel (i.e., more than one pixel), or another suitable
display element. Display element 90 includes a source 103 from
which the colorant particles enter the element display volume 100
and a sink 104 to which the colorant particles flow. During display
element 90 operation, the roles of source and sink can be reversed.
In other words, the source can become the sink and vice versa. The
flow lines 101 illustrate the movement of the colorant particles
from the source 103 to the sink 104 as described by the convective
movement of the carrier fluid.
The convective currents of display element 90 can be generated in
numerous ways. Convection is macroscopic movement of molecules in
fluids including liquids and gases. Convection is generated by
unbalanced volumetric forces inside the fluids that cause different
parts of the fluid to move relative to each other producing
convective currents. Convection can occur under gravity if
different parts of the fluid have different density caused, for
example, by localized heating. Convection can also occur if there
are pressure or concentration gradients inside the fluid produced
by localized chemical reactions, localized heating, or other
suitable disturbances. Convection can also occur if there are ionic
currents in the fluid caused by external electric fields (AC or DC)
and charge injection into the fluid. The moving ions then create
the pressure gradient through viscous drag and excluded volume
effects. Such convection is typically termed
electro-convection.
FIGS. 2A and 2B illustrate one embodiment of a method for
generating the convective flow within a display element 200. FIG.
2A illustrates display element 200 in a dark optical state. FIG. 2B
illustrates display element 200 in a clear optical state. Both
figures include a transparent top electrode 201 as the conceptual
"source" of FIG. 1 and another bottom electrode 205 as the
conceptual "sink" of FIG. 1. While the "source" electrode 201 of
FIG. 2 is subsequently described as being transparent, the present
embodiments are not required to have both electrodes as being
transparent. One of either the "source" or the "sink" electrodes
can be comprised of an opaque material.
The embodiment of FIGS. 2A and 2B, as well as the subsequently
described embodiments, include a "sink" electrode 205 formed on a
substrate that, in one embodiment, is coated with a continuous film
of transparent conductive material. The transparent conductive
material can include carbon nanotube layers, a transparent
conducting oxide such as ITO (Indium Tin Oxide), or a transparent
conducting polymer such as PEDOT (poly 3,4-ethylenedioxythiophene).
Other embodiments can use other materials that provide suitable
conductivity and transparency for display element 200.
In another embodiment, the substrate can be coated with or
comprised of a reflective material. In yet another embodiment, the
substrate can be an opaque material. In still another embodiment, a
light scatterer can be formed on the substrate.
A layer of transparent electrically insulating material 203 (i.e.,
dielectric material) is deposited on bottom electrode 205.
Dielectric layer 203 is patterned to create recessed regions 210 in
dielectric layer 203 on bottom electrode 205. The recessed regions
can be manufactured by many different processes. These processes
include embossing or imprinting with a master or stamp or etching
of dielectric layer 203. The recessed regions can be any suitable
size and/or shape.
In another embodiment, electrodes are only defined within the
recessed regions of dielectric layer 203. In such an embodiment,
dielectric layer 203 is deposited and patterned on top of the
insulating substrate first, and then the electrodes are formed
inside the recess areas, for example by electroless deposition or
by another suitable method. In another embodiment, bottom electrode
layer 205 is patterned into a collection of electrodes first, and
then dielectric layer 203 is deposited and recess areas 210 are
formed directly on top of the electrodes. The alignment for the
latter operation can be achieved for example by
photolithography.
Display element 200 is completed by the formation of transparent
"source" electrode 201 that is formed a fixed distance apart from
dielectric layer 203 to thus form display volume 204 that holds the
carrier fluid. The "source" electrode 201 is held at the fixed
distance by a network of mechanical stops (not shown) that may
include posts, walls, and/or spacer beads. The mechanical stops may
be formed by embossing, imprinting, molding, or photolithography of
materials such as photoresists or embossing resins.
The carrier fluid of FIGS. 2A and 2B, as well as the subsequently
described embodiments, can include either polar fluids (e.g. water)
or nonpolar fluids (e.g., dodecane). Additionally, anisotropic
fluids such as liquid crystal can be used. The fluid may include
surfactants such as salts, charging agents, stabilizers, and
dispersants. In one embodiment, the surfactants provide a fluid
that is an electrolyte that is able to sustain current by ionic
mass transport.
The colorant particles in the carrier fluid are comprised of a
charged material in the case of an electro-convective display. The
colorant particle material should be able to hold a stable charge
indefinitely so that repeated operation of the element does not
affect the charge on the colorant particles. Colorant particle
materials having a finite ability to hold a stable charge, however,
can be used in accordance with the various embodiments while they
maintain their charge.
In the dark optical state of display element 200, illustrated in
FIG. 2A, the colorant particles are relatively uniformly
distributed across the element's display volume 204 to absorb the
incident light and create the dark optical appearance. The colorant
particles may or may not be prevented from occupying one or more
recess regions 210 in dielectric layer 203.
To switch display element 200, an electric potential difference V
is applied between top electrode 201 and bottom electrode 205. This
results in a clearing of the main aperture of display element 200
as illustrated in FIG. 2B. Transverse solid lines of arrows
indicate electric field lines and arrows leading into the recess
regions indicate the flow of colorant particles following the
electrostatic and convective flows. Having the colorant particles
compacted in the recess regions is subsequently referred to as the
clear optical state.
Even though the electrical potential difference causes the ionic
and convective flow of the fluid, the charged colorant particles do
not follow the electric field lines (the solid lines). The charged
colorant particles actually follow the lines of convective flow as
shown by the dashed lines of FIG. 2B. In this regard, the flow is
not totally electrophoretic. Under purely electrophoretic flow, the
colorant particles would be pulled down vertically until stopped at
the top boundary of the dielectric but would not generally move
in-plane.
In one embodiment, the convective flow is induced by ionic mass
transport in the carrier fluid and charge transfer between the
carrier fluid and the electrodes. The charge transfer can occur
when the carrier fluid is coupled to the electrodes either through
direct contact with the electrodes or separated from the electrodes
by an intermediate layer including one or more materials. In the
latter case, charge transfer is facilitated by the internal
electrical conductivity of the intermediate layer, either
volumetric or via pinholes and other defects.
In another embodiment, the convective flow is a transient effect
caused by the ionic mass transport in the carrier fluid, but
without charge transfer between the carrier fluid and the
electrode. In this case, the convective flow proceeds for a finite
amount of time and facilitates the compaction of the colorant
particles in the recess areas. After that the colorant particles
are contained in the recesses by electrostatic forces generated by
a coupling with the electrodes.
To switch the display element from the clear optical state to the
dark optical state, the polarity of the voltage is reversed. This
induces convective flow in the opposite direction and the colorant
particles are no longer electrically contained in the recesses. As
a result, the colorant particles are mass transported to the
display volume and then spread relatively evenly throughout the
display volume.
Convection within the display element can also be induced by other
means. For example, convective flow can be induced by an
electrokinetic means, a mechanical means (e.g., mechanical
pistons), temperature gradients (e.g., heating of the sources and
sinks, focused radiation), chemical potential gradients, as well as
other means.
The depth of the recesses in the dielectric layer can be defined by
the following:
.times..times. ##EQU00001##
where: L is the colorant particle load by volume; Lm is the maximum
closed packed colorant particle load by volume; d is the thickness
of the main element display volume; and P is the aperture ratio
defined by 1-A.sub.0/A.
The quantity A is the area of the element display volume while
A.sub.0 is the recess area. The total area of the defined recess
regions of the first or second electrodes is sufficiently less than
the area of the display element to provide optical contrast between
the collected or clear particle state and the spread particle state
or grayscale state.
In one embodiment, the total area of the defined recess regions of
the first or second electrodes is between 1% and 10% of the area of
the display element, in order to maximize the optical contrast
between the clear and the dark or grayscale states. The present
embodiments, however, are not limited to any predefined aperture
ratio. For example, another embodiment might have a total area of
the recessed regions being between 10% and 20% of the area of the
display element. Still another embodiment might have a total area
of the recessed regions being between 20% and 50% of the area of
the display element. Other embodiments might have a total area of
the recessed regions being greater than 50% of the area of the
display element for embodiments where low optical contrast is
desired.
In additional embodiments, a grayscale of display element 200 can
be controlled by one of: an aperture ratio, a density of recess
regions that are electrically active, or a depth of recess regions
that are electrically active. These approaches enable geometrical
control over how the colorant particles are spread throughout the
display volume and collected in the recess regions through
variations in the sizes of the recess regions, the spacing between
the recess regions, and the depth of the recess regions. In one
embodiment, the aperture ratio P and the recess depth can be
adjusted to maximize the optical contrast between the clear and the
dark or grayscale optical states.
The present embodiments subsequently refer to a dot structure for
the recess regions or other methods for selectively patterning the
dielectric on at least one of the electrodes. A dot, for purposes
of the present embodiments, can be any shape and/or size as long as
it satisfies the requirements for the optical contrast and other
characteristics of the display element.
FIG. 3A illustrates a cross-sectional view of one embodiment of a
clear optical state of an electro-optical display element 300.
Electro-optical display element 300 includes a substrate 302, a
bottom electrode 304, a dielectric layer 306 including recess
regions 314, a display volume 308, a top electrode 310, and a
transparent material or substrate 312. In this embodiment, bottom
electrode 304 is a continuous, blanket, or solid plate electrode
formed on substrate 302. A dielectric layer is formed on bottom
electrode 304 and patterned to provide dielectric layer 306.
Dielectric layer 306 is patterned with recess regions 314 that
allow the charged colorant particles to compact.
Top electrode 310 is formed on transparent material 312. Top
electrode 310 is used to control the colorant particle
distributions, either with a uniform, segmented, or pixelated top
electrode as illustrated and described subsequently with reference
to FIGS. 4A and 4B.
In operation, positively charged ink can be electrophoretically and
convectively moved to bottom electrode 304, compacted into recess
regions 314, and held there by a negative bias in the clear optical
state. This results in a clear aperture. During a dark optical
state, illustrated in FIG. 3B, the positive bias on bottom
electrode 304 repels the positively charged colorant particles out
of recess regions 314 into the carrier fluid in the display volume
308. In addition, the convective currents speed up the movement of
particles and disburse the particles across display volume 308.
FIG. 4A illustrates a top view and FIG. 4B illustrates a
cross-sectional view of one embodiment of an electro-optical
display element 350 including a segmented or pixelated top
electrode. Electro-optical display element 350 includes a substrate
352, a bottom electrode 354, a dielectric layer 356 including
recess regions 368 and 370, a display volume 358, a segmented or
pixelated top electrode 360, and a transparent material or
substrate 366. Electro-optical display element 350 includes a dot
structure display. FIGS. 4A and 4B illustrate a segment, a
sub-pixel, or a super-pixel display element.
Display element 350 includes a periodic distribution of dots. Each
dot is a recess region 368 or 370 patterned into dielectric layer
356 to connect the display element display volume 358 to bottom
electrode 354. In the illustrated embodiment, bottom electrode 354
is a blanket electrode formed on substrate 352. Segmented or
pixelated top electrode 360 includes segments 361-363 and is formed
over display volume 358 on transparent material 366.
Each recess region 368 and 370 patterned into dielectric layer 356
is formed under a corresponding segmented or pixelated portion
361-363 of top electrode 360. The segmented or pixelated portions
361-363 of top electrode 360 are electrically disconnected thus
allowing each corresponding segmented or pixelated portion 361-363
to have a different polarity than an adjacent portion 361-363.
There may be multiple recess regions under each corresponding
segmented or pixelated portion 361-363 of top electrode 360 but,
for simplicity, only one recess region is shown under each
segmented or pixelated portion 361-363 in the figure.
Electro-optical display element 350 illustrates adjacent display
elements in the light and dark optical states. In operation,
assuming that the colorant particles are positively charged, if a
negative voltage is applied to the segmented or pixelated portions
361 and 363 of top electrode 360, the colorant particles are
attracted out of recess regions 368 into the carrier fluid in
display volume 358. The center segmented or pixelated portion 362
of top electrode 360, however, has a positive voltage and thus the
colorant particles are compacted in recess regions 370 making that
portion of the segment or pixel clear. This method can be used to
control the state of each segment or pixel.
FIGS. 4A and 4B illustrate that top electrode 360 is segmented or
pixelated. In another embodiment, bottom electrode 354 is segmented
or pixelated instead of top electrode 360. In yet another
embodiment, both top electrode 360 and bottom electrode 354 are
segmented or pixelated. In another embodiment, one or more
additional electrodes can be formed between top electrode 360 and
bottom electrode 354. Such additional electrodes can be used to
shape the electric fields and control the translation of colorant
particles.
FIG. 5 illustrates one embodiment of a static grayscale patterning
technique for an electro-optical display device. In one embodiment,
a static grayscale image is generated in an electro-optical display
device by removing portions of an electrode of the display device.
In one embodiment, a portion of top electrode 310 previously
described and illustrated with reference to FIGS. 3A and 3B or a
portion of top electrode 360 previously described and illustrated
with reference to FIGS. 4A and 4B may be removed as indicated in
FIG. 5 to produce a static grayscale image. In another embodiment,
a portion of bottom electrode 304 previously described and
illustrated with reference to FIGS. 3A and 3B or a portion of
bottom electrode 354 previously described and illustrated with
reference to FIGS. 4A and 4B may be removed as indicated in FIG. 5
to produce a static grayscale image. In another embodiment,
dielectric layer 306 previously described and illustrated with
reference to FIGS. 3A and 3B is patterned or dielectric layer 356
previously described and illustrated with reference to FIGS. 4A and
4B is patterned as indicated in FIG. 5 to produce a static
grayscale image.
The lines in FIG. 5 illustrate the ITO, PEDOT, or conductive
material that has been removed from the electrode or the dielectric
material that has been removed or has not been recess patterned
within the dielectric layer. The percent values in FIG. 5 indicate
how much ITO, PEDOT, or conductive material of the electrode
remains in a given area or how much dielectric material remains in
a given area.
At 400, 40% of the dielectric material or 40% of the ITO, PEDOT, or
conductive material of the electrode remains. At 402, 50% of the
dielectric material or 50% of the ITO, PEDOT, or conductive
material of the electrode remains. At 404, 62.5% of the dielectric
material or 62.5% of the ITO, PEDOT, or conductive material of the
electrode remains. At 406, 66.7% of the dielectric material or
66.7% of the ITO, PEDOT, or conductive material of the electrode
remains. At 408, 70% of the dielectric material or 70% of the ITO,
PEDOT, or conductive material of the electrode remains. At 410, 75%
of the dielectric material or 75% of the ITO, PEDOT, or conductive
material of the electrode remains. At 412, 80% of the dielectric
material or 80% of the ITO, PEDOT, or conductive material of the
electrode remains. At 414, 85% of the dielectric material or 85% of
the ITO, PEDOT, or conductive material of the electrode remains. At
416, 90% of the dielectric material or 90% of the ITO, PEDOT, or
conductive material of the electrode remains. By controlling the
amount of dielectric material or ITO, PEDOT, or conductive material
of the electrode removed in a given area, the grayscale is
controlled.
FIG. 6 illustrates another embodiment of a static grayscale
patterning technique for an electro-optical display device. In this
embodiment, a static grayscale image is generated by removing dots
of ITO, PEDOT, or conductive material of the electrode or by
removing dots of dielectric material from the dielectric layer. The
dots of dielectric material removed may be uniform as illustrated
in FIG. 6 or stochastic. The dots in FIG. 6 illustrate the ITO,
PEDOT, or conductive material that has been removed from the
electrode or the dielectric material that has been removed or has
not been recess patterned from the dielectric layer. The percent
values in FIG. 6 indicate how much ITO, PEDOT, or conductive
material of the electrode remains in a given area or how much
dielectric material remains in a given area.
At 450, 40% of the dielectric material or 40% of the ITO, PEDOT, or
conductive material of the electrode remains. At 452, 50% of the
dielectric material or 50% of the ITO, PEDOT, or conductive
material of the electrode remains. At 454, 62.5% of the dielectric
material or 62.5% of the ITO, PEDOT, or conductive material of the
electrode remains. At 456, 66.7% of the dielectric material or
66.7% of the ITO, PEDOT, or conductive material of the electrode
remains. At 458, 70% of the dielectric material or 70% of the ITO,
PEDOT, or conductive material of the electrode remains. At 460, 75%
of the dielectric material or 75% of the ITO, PEDOT, or conductive
material of the electrode remains. At 462, 80% of the dielectric
material or 80% of the ITO, PEDOT, or conductive material of the
electrode remains. At 464, 85% of the dielectric material or 85% of
the ITO, PEDOT, or conductive material of the electrode remains. At
466, 90% of the dielectric material or 90% of the ITO, PEDOT, or
conductive material of the electrode remains. By controlling the
amount of dielectric material or ITO, PEDOT, or conductive material
of the electrode removed in a given area, the grayscale is
controlled.
While FIG. 5 illustrates removing lines of dielectric material or
ITO, PEDOT, or conductive material to control the grayscale level
and FIG. 6 illustrates removing dots of dielectric material or ITO,
PEDOT, or conductive material to control the grayscale level, in
other embodiments combinations of uniform or stochastic lines and
dots, or other suitable shapes, can be used to create the desired
level of grayscale in a given area.
The ITO, PEDOT, or conductive material can be removed in a number
of different ways, such as by laser delamination, laser ablation,
or wet or dry etching and photo-patterning. In one embodiment, a
laser and optional collimation optics and intensity conversion
optics are used in combination with a galvanometer with lens, which
receives input from computer drawing files, to pattern the ITO,
PEDOT, or conductive material in a fixed work plane. This
embodiment enables a patterning size up to the field of view (FOV)
of the galvanometer lens. In another embodiment, a laser and
optional collimation optics and intensity conversion optics are
used in combination with a galvanometer with lens, which receives
input from computer drawing files, to pattern the ITO, PEDOT, or
conductive material in a work plane with motion. In this
embodiment, multiple drawing files are stitched together allowing a
patterning size up to the range of motion with substrate. The
galvanometer writes within its FOV, then the motion steps the
substrate to the next field.
In another embodiment, a laser and optional collimation optics and
intensity conversion optics are used in combination with a fixed
focusing lens, which receives input from computer drawing files, to
pattern the ITO, PEDOT, or conductive material in a work plane with
motion. In this embodiment, multiple drawing files are stitched
together allowing a patterning size up to the range of motion with
substrate. In another embodiment, a laser and collimation optics, a
homogenizer, and photomasks are used in combination with an imaging
projection lens to pattern the ITO, PEDOT, or conductive material
in a work plane with motion. In this embodiment, multiple
photomasks can be inserted that are stitched together allowing a
patterning size up to the range of motion with substrate. Each
photomask can be fixed or scanned.
In another embodiment, a photolithography process is used to
pattern the ITO, PEDOT, or conductive material. In this embodiment,
photoresist is applied to an ITO, PEDOT, or conductive material
substrate and photo patterned, developed, and rinsed to pattern the
ITO, PEDOT, or conductive material. This embodiment enables
patterning on wafer sized substrates.
In another embodiment, a roll to roll process is used to pattern
the ITO, PEDOT, or conductive material. In this embodiment,
embossing resin is applied to the roll of ITO, PEDOT, or conductive
material and the grayscale pattern is embossed using an embossing
roller. The patterned embossing resin provides a mask for etching
the ITO, PEDOT, or conductive material. After etching the ITO,
PEDOT, or conductive material, the embossing resin is removed. In
other embodiments, other suitable processes are used to pattern the
ITO, PEDOT, or conductive material.
In other embodiments, similar processes are used to pattern the
dielectric layer. In one embodiment, the dielectric layer is
patterned via photopatterning using a uniform dot patterned mask
and a grayscale image patterned mask such that areas where recessed
regions are not wanted are exposed.
FIG. 7A illustrates a cross-sectional view of one embodiment of a
grayscale optical state of an electro-optical display element 500.
Electro-optical display element 500 includes a substrate 502, a
bottom electrode 504, a dielectric layer 506 including recess
regions 514, a display volume 508, a patterned top electrode 510,
and a transparent material or substrate 512. In this embodiment,
top electrode 510 is patterned to provide a static grayscale image
based on the ratio of removed and conductive regions of the
electrode.
In one embodiment, substrate 502 includes a reflective material or
an optically clear or transparent material, such as plastic (e.g.,
polyethylene terephthalate (PET)) or other suitable material. In
one embodiment, transparent material or substrate 512 also includes
an optically clear material, such as plastic (e.g., PET) or other
suitable material. Bottom electrode 504 and top electrode 510
include inorganic materials such as ITO, organic materials such as
PEDOT, nanoparticle networks such as carbon nanotubes or silver
nanowires, or other suitable thin film conductive materials that
can be patterned. Dielectric material 506 includes an optically
clear or transparent electrically insulating material.
In operation, the grayscale state as illustrated in FIG. 7A is
provided by applying a negative bias or voltage signal to top
electrode 510 (for positively charged colorant particles). The
negative bias to top electrode 510 attracts the colorant particles
out of recess regions 514 into the carrier fluid adjacent the
segments of top electrode 510 in display volume 508. In this way, a
static, pre-patterned grayscale image is displayed.
In another embodiment, dielectric layer 506 is excluded from
electro-optical display element 500. In this embodiment, the
grayscale state as illustrated in FIG. 7A is still provided by
applying the negative bias or voltage signal to top electrode 510.
A clear state, however, as discussed below with reference to FIG.
7C is not possible with dielectric layer 506 excluded since there
are no recess regions 514 in which the colorant particles can be
compacted.
FIG. 7B illustrates a cross-sectional view of one embodiment of a
dark optical state of electro-optical display element 500. The dark
optical state is achieved from either the grayscale optical state
or the clear optical state by applying a voltage signal or pulsing
opposite bias conditions on bottom electrode 504 and top electrode
510 to spread the colorant particles into display volume 508. With
the colorant particles diffused uniformly within the display volume
508, the dark state is displayed.
FIG. 7C illustrates a cross-sectional view of one embodiment of a
clear optical state of electro-optical display element 500. The
clear optical state is achieved by applying a compacting negative
bias condition or voltage signal to bottom electrode 504 such that
the colorant particles are compacted within recess regions 514.
FIG. 8A illustrates a cross-sectional view of one embodiment of a
grayscale optical state of an electro-optical display element 600.
Electro-optical display element 600 includes a substrate 602, a
bottom electrode 604, a dielectric layer 606 including recess
regions 614, a display volume 608, a top electrode 610, and a
transparent material or substrate 612. In this embodiment, bottom
electrode 604 and top electrode 610 are continuous or blanket
electrodes. Dielectric layer 606 is patterned to provide a static,
pre-patterned grayscale image based on the ratio of exposed and
covered regions of bottom electrode 604.
In one embodiment, substrate 602 includes a reflective material or
an optically clear or transparent material, such as plastic (e.g.,
PET) or other suitable material. In one embodiment, transparent
material or substrate 612 also includes an optically clear
material, such as plastic (e.g., PET) or other suitable material.
Bottom electrode 604 and top electrode 610 include inorganic
materials such as ITO, organic materials such as PEDOT,
nanoparticle networks such as carbon nanotubes or silver nanowires,
or other suitable thin film conductive materials that can be
patterned. Dielectric material 606 includes an optically clear or
transparent electrically insulating material.
For positively charged colorant particles, bottom electrode 604
with shade patterned dielectric layer 606 can hold the colorant
particles according to the pattern when a small negative holding
bias or voltage signal is applied to bottom electrode 604. In this
state, some of the colorant particles are held in recess regions
614 while some of the colorant particles, which are away from
recess regions 614, remain in display volume 608. The ratio of the
blocked and open regions of dielectric layer 606 determines the
static, pre-patterned grayscale image.
FIG. 8B illustrates a cross-sectional view of one embodiment of a
dark optical state of electro-optical display element 600. The dark
optical state is achieved from either the grayscale optical state
or the clear optical state by applying a voltage signal or pulsing
opposite bias conditions on bottom electrode 604 and top electrode
610 to spread the colorant particles into display volume 608. With
the colorant particles diffused uniformly within the display volume
608, the dark optical state is displayed.
FIG. 8C illustrates a cross-sectional view of one embodiment of a
clear optical state of electro-optical display element 600. The
clear optical state is achieved by applying a larger compacting
negative bias condition or voltage signal to bottom electrode 604
than the negative bias condition applied for the grayscale optical
state previously described and illustrated with reference to FIG.
8A. This method may not be as effective in compacting all the
colorant particles since the number of recess regions for
compacting the colorant particles may be reduced. In another
embodiment, dielectric layer 606 includes uniform dot recess
regions and bottom electrode 604 is patterned to provide the
desired grayscale level.
FIG. 9 illustrates a cross-sectional view of one embodiment of
stacking grayscaled primary colorant layers for full color static
images. Single color display element 700 includes a substrate 702,
a bottom electrode 704, a dielectric layer 706 including recess
regions 716, a display volume 708, yellow colorant particles 710, a
patterned top electrode 712, and a transparent material 714. Single
color display element 720 includes a substrate 722, a bottom
electrode 724, a dielectric layer 726 including recess regions 736,
a display volume 728, magenta colorant particles 730, a patterned
top electrode 732, and a transparent material 734. Single color
display element 740 includes a substrate 742, a bottom electrode
744, a dielectric layer 746 including recess regions 756, a display
volume 748, cyan colorant particles 750, a patterned top electrode
752, and a transparent material 754.
Each single color display element 700, 720, and 740 provides
monochrome information for the desired static image. The grayscale
images are different for each primary color and are tuned following
correlational curves for proper grayscale levels for each primary
color. The individual colorant layers are produced and then brought
together to provide a full color display element 760 for displaying
the full color static image. The full color static image is
displayed when each of electrodes 712, 732, and 752 are biased to
attract colorant particles 710, 730, and 750, respectively, as
illustrated in FIG. 9. In other embodiments, two (e.g., CM), four
(e.g. CYMK), or another suitable number of single color display
elements are combined to provide a multicolor display. While FIG. 9
illustrates producing a static grayscale image by patterning the
top electrode of each colorant layer, in other embodiments the
grayscale image for each colorant layer is produced by using
display elements as previously described and illustrated with
reference to FIGS. 3A-8C.
FIG. 10A illustrates a cross-sectional view of one embodiment of a
full color transmissive static display 800. Display 800 includes a
cyan display element 802, a magenta display element 804, and a
yellow display element 806. Magenta display element 804 is stacked
on cyan display element 802, and yellow display element 806 is
stacked on magenta display element 804. Each display element 802,
804, and 806 includes a transparent substrate, transparent bottom
and top electrodes, a transparent dielectric layer, and a display
volume as previously described and illustrated with reference to
FIG. 9.
The combination of colored display elements 802, 804, and 806
provide a static full color image as indicated by arrows 808, 810,
812, 814, and 816. Arrow 808 indicates a first color provided by
light passing through the colorant particles of yellow display
element 806. Arrow 810 indicates a second color provided by light
passing through the colorant particles of yellow display element
806 and magenta display element 804. Arrow 812 indicates a third
color provided by light passing through the colorant particles of
magenta display element 804 and cyan display element 802. Arrow 814
indicates a fourth color provided by light passing through the
colorant particles of cyan display element 802. Arrow 816 indicates
a fifth color provided by light passing through the colorant
particles of magenta display element 804.
FIG. 10B illustrates a cross-sectional view of one embodiment of a
full color reflective static display 850. Display 850 includes a
cyan display element 802, a magenta display element 804, and a
yellow display element 806. Magenta display element 804 is stacked
on cyan display element 802, and yellow display element 806 is
stacked on magenta display element 804. Each display element 802,
804, and 806 includes a transparent substrate, transparent bottom
and top electrodes, a transparent dielectric layer, and a display
volume as previously described and illustrated with reference to
FIG. 9. In addition, display 850 includes a white reflector 820 on
the bottom of the substrate of cyan display element 802. Thus, in
this embodiment, the combination of colored display elements 802,
804, and 806 with white reflector 820 provide a static full color
reflected image as indicated by arrows 808, 810, 812, 814, and 816,
which represent the same colors as previously described and
illustrated with reference to FIG. 10A.
Embodiments provide static grayscale images for electro-optical
display devices. Embodiments can be used to provide reflective,
monochrome, black and white, or color displays. Embodiments can
also be used to provide transmissive monochrome, black and white,
or color displays. In addition, embodiments can be used to provide
backlit electrophoretic monochrome, black and white, or color
displays. The embodiments have multiple applications for apparel,
marketing, handheld electronics, lap-top computers, lighting,
etc.
Although specific embodiments have been illustrated and described
herein, it will be appreciated by those of ordinary skill in the
art that a variety of alternate and/or equivalent implementations
may be substituted for the specific embodiments shown and described
without departing from the scope of the present disclosure. This
application is intended to cover any adaptations or variations of
the specific embodiments discussed herein. Therefore, it is
intended that this disclosure be limited only by the claims and the
equivalents thereof.
* * * * *